Results of shell model calculations for Ni-76 and Ni-78 with newly derived effective interaction for the f(5/2)p(3/2)p(1/2)g(9/2) and the f(7/2)f(5/2)p(3/2)p(1/2)g(9/2) model spaces are presented. The calculated spectra of 76Ni in different spaces are compared and the role of the Ni-56 core breaking is discussed. Calculated half-life and branching ratios for beta-decay of Ni-78 and the effect associated with the f(7/2) orbital are analyzed.

Resonant elastic scattering of a radioactive $^{20}\mathrm{Na}$ beam incident upon protons in a polyethylene target has been used to probe the level structure of $^{21}\mathrm{Mg}$ above the proton decay threshold. Three states have been observed, and their properties deduced through analysis based on the R-matrix formalism. The results improve and extend previous studies of this nucleus. An estimate of the $^{20}\mathrm{Na}$(p,\ensuremath{\gamma})$^{21}\mathrm{Mg}$ reaction rate, including these new data, suggests this reaction will not play a significant role in explosive hydrogen burning in astrophysical sites such as novae and x-ray bursts.

We carry out a systematic analysis of angular distribution measurements for selected ground-state to ground-state (d,p) and (p,d) neutron transfer reactions, including the calcium isotopes. We propose a consistent three-body model reaction methodology in which we constrain the transferred-neutron bound state and nucleon-target optical potential geometries using modern Hartree-Fock calculations. Our deduced neutron spectroscopic factors are found to be suppressed by similar to 30% relative to independent-particle shell-model values, from Ca-40 through Ca-49. The other nuclei studied, ranging from B to Ti, show similar average suppressions with respect to large-basis shell-model expectations. Our results are consistent with deduced spectroscopic strengths for neutrons and protons from intermediate-energy nucleon knockout reactions and for protons from (e,e(')p) reactions on well-bound nuclei.

The odd-odd fp-shell nucleus Sc-52 was investigated using in-beam gamma-ray spectroscopy following secondary fragmentation of a V-55 and Cr-57 cocktail beam. Aside from the known gamma-ray transition at 674(5) keV, a new decay at E-gamma=212(3) keV was observed. It is attributed to the depopulation of a low-lying excited level. This new state is discussed in the framework of shell-model calculations with the GXPF1, GXPF1A, and KB3G effective interactions. These calculations are found to be fairly robust for the low-lying level scheme of Sc-52 irrespective of the choice of the effective interaction. In addition, the frequency of spin values predicted by the shell model is successfully modeled by a spin distribution formulated in a statistical approach with an empirical, energy-independent spin-cutoff parameter.

Proton and neutron densities from Skyrme-Hartree-Fock calculations of a number of nuclei with masses ranging from 28 to 58 have been used to generate optical potentials for proton elastic scattering. Those potentials, generated by folding the structure functions with effective in-medium nucleon-nucleon (NN) interactions, have been used to evaluate proton total reaction cross sections; cross sections that reveal signatures of the structures.

Data from three gamma spectroscopy experiments using deep-inelastic heavy ion reactions provided new information on high-spin states in the Ca-48 core nucleus and in the N=30, Ca-50 and Sc-51 isotones. Shell model calculations restricted to neutron excitations only are shown to reproduce with good accuracy some of the experimental levels. It is demonstrated that proton excitations not accounted in these calculations are abundantly present in the observed yrast structures. High energy of the 4(+) state in Ca-50 underlines the validity of the N=32 shell closure.

The predicted and experimental properties of the new doubly magic nuclei {sup 22}O and {sup 24}O are discussed. These together with previous observations lead to a new rule for magic numbers: if there is an oscillator magic number (2, 8, 20, or 40) for one kind of nucleon, then the other kind of nucleon has a magic number for the filling of every possible (n, l, j) value.

To address the question of collectivity in neutron-rich nuclei near N=28, an inverse kinematics inelastic proton scattering experiment has been performed. Confirmation of excited states in Si-36,Si-38 has been made. The path from excitation cross-section to deformation parameter is outlined.

The results of the shell model calcualtions for even Ni68-76 isotopes with newly derived effective interaction for the f(5/2)p(3/2)p(1/2)g(9/2)model space are presented. The differences in the structure of Ni68-78 isotopes and corresponding valence mirror symmetry partners, A = 90 - 98 N = 50, isotones are indicated. The origin of the differences are identified and related to the properties of the effective interactions.

Data from three gamma spectroscopy experiments using deep-inelastic heavy ion reactions provided new information on high-spin states in the neutron-rich N = 30, Ca-50 and Sc-51 isotones. Shell model calculations restricted to neutron excitations only are shown to reproduce with good accuracy some of the experimental levels. It is demonstrated that proton excitations not accounted in these calculations are abundantly present in the observed yrast structures. High energy of the 4(+) state in Ca-50 underlines the validity of the N = 32 shell closure.

The beta decay of Sn-135 was studied at CERN/ISOLDE using a resonance ionization laser ion source and mass separator to achieve elemental and mass selectivity, respectively. gamma-ray singles and gamma-gamma coincidence spectra were collected as a function of time with the laser on and with the laser off. These data were used to establish the positions of new levels in Sb-135, including new low-spin states at 440 and 798 keV, which are given tentative spin and parity assignments of 3/2(+) and 9/2(+), respectively. The observed levels of Sb-135 are compared with shell-model calculations using different single-particle energies and different interactions.

Shell-model calculations in the $s\ensuremath{-}d$ shell have been utilized to examine how the statistical behavior of eigenvalues and reduced transition probabilities are affected by broken isospin symmetry. Calculations have been performed for the nuclides $^{22}\mathrm{Na},^{26}\mathrm{Al}$, and $^{34}\mathrm{Cl}$ and have been compared to existing experimental data for $^{26}\mathrm{Al}$ and $^{30}\mathrm{P}$. The eigenvalue statistics depend on the magnitude of the Coulomb matrix element, and this is reflected in a sensitivity to the choice of single-particle energies. The distributions of reduced transition probabilities are not universal but depend upon the particular transition mode chosen; this behavior is qualitatively similar to experimental results.

The B(E2;0(+)(1)-->2(+)(1)) values for the radioactive neutron-rich germanium isotopes (78,80)Ge and the closed neutron shell nucleus 82Ge were measured at the HRIBF using Coulomb excitation in inverse kinematics. These data allow a study of the systematic trend between the subshell closures at N=40 and 50. The B(E2) behavior approaching N=50 is similar to the trend observed for heavier isotopic chains. A comparison of the experimental results with a shell model calculation demonstrates persistence of the N=50 shell gap and a strong sensitivity of the B(E2) values to the effective interaction.

The $^{9}\mathrm{Be}(^{46}\mathrm{Ar},^{45}\mathrm{Ar}+\ensuremath{\gamma})X$ one-neutron removal reaction has been studied in inverse kinematics at 70 MeV/nucleon. Coincidences with \ensuremath{\gamma} rays served to disentangle knockout events leading to the $^{45}\mathrm{Ar}$ ground state. The measured partial cross section corresponds to a spectroscopic factor of 4.9(7). The residue momentum distribution is compared with new calculations based on eikonal theory and represents the first case of an $\ensuremath{\ell}=3$ neutron removal, as is expected for populating a $0{f}_{7/2}$ hole in the $N=28$ projectile. However, the measured $^{45}\mathrm{Ar}$ momentum distribution has a marked low-momentum tail suggestive of dissipative effects whereas the eikonal model predictions are symmetric. The angular distribution of the residues confirms that there is a deviation from the model.

The even Ti52-56 isotopes have been studied with intermediate-energy Coulomb excitation and absolute B(E2;0(+)-> 2(1)(+)) transition rates have been obtained. These data confirm the presence of a subshell closure at neutron number N=32 in neutron-rich nuclei above the doubly magic nucleus Ca-48 and provide no direct evidence for the predicted N=34 closure. Large-scale shell model calculations with the most recent effective interactions are unable to reproduce the magnitude of the measured strengths in the semimagic Ti nuclei and their strong variation with neutron number.

Nuclear moments of odd-A neon isotopes in the range 17 <= A <= 25 have been determined from optical hyperfine structures measured by collinear fast-beam laser spectroscopy. The magnetic dipole moments of Ne-17, Ne-23, and Ne-25, as well as the electric quadrupole moment of Ne-23, are either reported for the first time or improved considerably. The measurements also decide for a 1/2(+) ground state of Ne-25. The behavior of the magnetic moments of the proton drip-line nucleus Ne-17 and its mirror partner N-17 suggests isospin symmetry. Thus, no clear indication of an anomalous nuclear structure is found for Ne-17. The magnetic moments of the investigated nuclei are discussed in a shell-model approach.

The Cl-32(p,gamma)Ar-33 reaction rate is of potential importance in the rp process powering type I x-ray bursts. Recently, Clement [Phys. Rev. Lett. 92, 172502 (2004)] [1] presented new data on excitation energies for low-lying proton unbound states in Ar-33 obtained with a new method developed at the National Superconducting Cyclotron Laboratory. We use their data, together with a direct capture model and a shell model calculation, to derive a new reaction rate for use in astrophysical model calculations. In particular, we take into account capture on the first excited state in Cl-32, and we also present a realistic estimate of the remaining uncertainties. We find that the Cl-32(p,gamma)Ar-33 reaction rate is dominated entirely by capture on the first excited state in Cl-32 over the whole temperature range relevant in x-ray bursts. In the temperature range from 0.2 to 1 GK the rate is up to a factor of 70 larger than the previously recommended rate based on shell model calculations only. The uncertainty is now reduced from up to a factor of 1000 to a factor of 3 at 0.3-0.7 GK and a factor of 6 at 1.5 GK.

In an experiment at the SISSI/LISE3 facility of GANIL, we have studied the decay of the two proton-rich nuclei Fe-45 and Ni-48. We identified 30 implantations of Fe-45 and observed for the second time four implantation events of Ni-48. In 17 cases, Fe-45 decays by two-proton emission with a decay energy of 1.154(16) MeV and a half-life of T-1/2=1.6(-0.3)(+0.5) ms. The observation of Ni-48 and of its decay allows us to deduce a half-life of T-1/2=2.1(-0.7)(+2.1) ms. One out of four decay events is completely compatible with two-proton radioactivity and may therefore indicate that Ni-48 has a two-proton radioactivity branch. We discuss all information now available on two-proton radioactivity for Fe-45 and Ni-48 and compare it to theoretical models.

We discuss the history of the USD interaction for the sd-shell and the progress for determining a new interaction by the inclusion of a more complete set of experimental data including the new data that has accumulated over the last 20 years.

Gamma rays from neutron-rich Ti nuclei in the vicinity of N = 32 have been studied at Gammasphere using deep-inelastic reactions induced by a 305 MeV Ca-48 beam on a thick Pb-208 target. The yrast gamma-ray cascades in Ti-53 were identified for the first time and the location in energy of the states with spin up to J=21/2 was determined. The yrast excitations of Ti-53, together with the earlier studied yrast structure of Ti-54, provided new tests of effective interactions for full pf-shell calculations. The data confirm the presence of a significant subshell gap at N=32. Comparisons between theory and experiment regarding the highest spin states located in Ti-53,Ti-54 suggest that energy gap at N=34 in neutron-rich nuclei is not as large as predicted by the recently proposed GXPF1 interaction.